Campbell Scientific CPEC200 Closed-Path Eddy-Covariance System - Manual (Page 32)

CPEC200 Closed-Path Eddy-Covariance System
FIGURE 5-5. Connecting pump tube from EC155 analyzer to pump
module
5.2.2 Zero/Span
The CPEC200 can perform automated zero (CO
2
and H
2
O) and CO
2
span of
the EC155. In most cases the user must supply cylinders of zero air and CO
2
span gas with appropriate regulators. If the user has chosen the optional
CPEC200 scrub module, then no cylinder of zero air is required. The rest of
this section assumes the use of cylinders of compressed gas, but see Appendix
G, CPEC Scrub Module Installation, Operation and Maintenance, for details
on the scrub module. Install cylinders in close proximity to the CPEC200
system enclosure. Each cylinder must have a pressure regulator to control the
outlet pressure at 10 psig and must have a 1/4-in Swagelok ® fitting on the
outlet. Connect regulators to the valve module inlets using 1/4-in OD tubing,
such as pn 15702, or pre-swaged tube assemblies (pn 21823-L). Minimize the
length of these tubes to reduce the equilibration time after the zero or CO
2
span
cylinder is selected. Refer to Appendix E, Using Swagelok ® Fittings, for
information on installing and replacing Swagelok ® fittings.
Flow meters and needle valves are not needed because the
CPEC200 valve module has a proportional-control valve to
actively control the flow of zero and span gas to the EC155.
NOTE
22